The present invention relates to telephone systems, and more particularly, to a system which requires no central office and which is simple and relatively inexpensive to install and use.
The system is particularly suitable for use in mines, although its usefulness is obviously not limited to this particular application and it is capable of use generally in any desired location. There is a need for improved communication equipment in the mining industry which could contribute significantly to improved safety and working conditions as well as to increased productivity. A mine presents an extremely harsh environment and equipment for use in a mine must be able to withstand rough treatment in use as well as exposure to coal dust and rock dust and to high humidity or dripping water. Such equipment must be capable of use by miners and its operation should, therefore, be simple and as much like that of the familiar public telephone system as possible. Such a telephone system should also be reasonable in cost and easy to install and to maintain, and for safety reasons should provide at least one private channel.